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www.nasa.gov www.bradley.ed u International Space Station (ISS) is a research facility assembled in low Earth orbit. (~220 miles or 354 km from Earth) The ISS project is a multi-national effort led by United States, with partners from Russia, Canada, the European Union, Japan, and others. Construction of the ISS began in 1998 and completed in 2011 with operations to continue until at least 2015, and likely 2020+ ISS is the largest artificial satellite that has ever orbited the Earth, it can be seen with a naked eye

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www.nasa.gov www.bradley.ed u ISS is much longer than the length of Boeing 777. It is larger than 5BR house, weigh ~ 1 million lbs, and its 16 solar panels generate ~84 kW and cover more than 3 times the US Senate Chamber Since First Launch Nov 20, 1998 –More than 1.8 billion statute miles on the odometer. –~10 round trips to the Sun –~70,000 orbits around the Earth –More than 105 launches to ISS –More than 200 visitors to ISS from 8 different countries –67 Russian vehicles, 36 space shuttles, 2 European, 1 Japanese –More than 150 Spacewalks

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www.nasa.gov www.bradley.ed u Results of the LIT Tests During LIT 1-9 the average number cycles for lubricant to become ineffective was 29,200 cycles using first pair of rollers. During LIT 10-18 experiments the average number cycles for lubricant to become ineffective was 60,400 cycles.

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www.nasa.gov www.bradley.ed u Results of the LIT Tests During the LIT1-9 experiments there were more than 885,000 rotations using the first pair of rollers. During LIT 10-19 there were more than 850,000 rotations without significant damage to render the rollers functionless. Note: SARJ makes nearly 96,000 rotations per year.

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www.nasa.gov www.bradley.ed u 39 Summary SARJ was vulnerable to inadequate lubrication Large friction can produce SARJ roller tipping Relative effects of operating parameters were studied by test Loss of lubrication effectiveness was determined from the rise of the axial force to a critical value The most influential parameter was the mass of grease applied “Strategic pauses” were effective to extend lube effectiveness in the VRR and be an effective strategy for SARJ

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www.nasa.gov www.bradley.ed u 45 Spacewalks to Clean and Lubricate the SARJ Mechanisms were Successful, and Systems are Operating Well Will the SARJ mechanism require additional applications of grease ? Can we expect “warning signs” that the lubrication condition is becoming inadequate?